Fix Windows Defender Service Not Starting

Having trouble with your Windows Defender service not starting? Let’s dive into effective solutions to resolve this issue.

Troubleshooting Windows Defender Service Start Issues

If you are experiencing issues with the Windows Defender service not starting, there are a few troubleshooting steps you can try to resolve the problem.

1. Check User Account Control (UAC) settings: Ensure that UAC is not blocking the Windows Defender service from starting. To do this, follow these steps:
a. Press the Windows key + R to open the Run dialog box.
b. Type msconfig and press Enter.
c. In the System Configuration dialog box, click on the Tools tab.
d. Scroll down and select Change UAC Settings.
e. Make sure the UAC slider is set to Never Notify.
f. Click OK and restart your computer.

2. Run System File Checker (SFC) scan: The SFC tool scans for and repairs corrupt system files that may be causing the Windows Defender service startup issue. Here’s how to run an SFC scan:
a. Press the Windows key + X and select Command Prompt (Admin).
b. Type sfc /scannow and press Enter.
c. Wait for the scan to complete and restart your computer.

3. Check Windows Registry: Incorrect or missing registry entries can prevent the Windows Defender service from starting. Follow these steps to check the Windows Registry:
a. Press the Windows key + R to open the Run dialog box.
b. Type regedit and press Enter.
c. In the Registry Editor, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender.
d. Check if there is a DisableAntiSpyware value. If it exists, set its value to 0.
e. Close the Registry Editor and restart your computer.

Methods to Resolve Windows Defender Service Not Starting

• Press Windows + R to open the Run dialog box.
• Type services.msc in the Run dialog box, then press Enter.
• Scroll down and locate Windows Defender Firewall in the list of services.
• Right-click on Windows Defender Firewall and select Restart.
  
• If the service is already running, select Stop and then Start it again.
• Close the Services window and check if the issue is resolved.
  

Method 2: Set Windows Defender Service to Automatic

• Open the Run dialog box by pressing Windows + R.
• Type services.msc and hit Enter.
• Scroll down and find Windows Defender Firewall in the list of services.
• Right-click on Windows Defender Firewall and select Properties.
  
• In the Properties window, go to the General tab.
• Under Startup type, select Automatic.
• Click on Apply and then OK.
• Restart your computer and check if the issue is resolved.

Method 3: Perform a System File Check

• Press Windows + X and select Command Prompt (Admin) or Windows PowerShell (Admin).
• In the Command Prompt window, type sfc /scannow and press Enter.
• Wait for the scan to complete. It may take some time.
• If any corrupted system files are found, the tool will attempt to repair them automatically.
• Once the scan is finished, restart your computer and check if the issue is resolved.

Method 4: Disable Third-Party Antivirus

• Open the settings of your third-party antivirus program.
• Look for an option to disable or turn off the antivirus temporarily.
• Disable the antivirus and save the changes.
• Restart your computer and check if Windows Defender Service starts properly.

Steps to Repair Windows Defender Service on Windows PCs

1. Open the Command Prompt with administrative privileges by pressing the Windows key and typing “Command Prompt” into the search bar. Right-click on the Command Prompt app and select “Run as administrator” from the context menu.

2. In the Command Prompt window, type “sc queryex WinDefend” and press Enter. This command will display the current status of the Windows Defender service.

3. If the status of the Windows Defender service is not “Running,” you can try to start it manually. Type “sc start WinDefend” and press Enter. This command will attempt to start the Windows Defender service.

4. If the Windows Defender service still does not start, you can try using the System File Checker tool to repair any corrupted system files. In the Command Prompt window, type “sfc /scannow” and press Enter. This command will scan your system for corrupted files and attempt to repair them.

5. After running the System File Checker tool, restart your computer and check if the Windows Defender service starts automatically. If not, you can try to reset the Windows Defender settings. Open the Command Prompt with administrative privileges again and type “Set-MpPreference -DisableRealtimeMonitoring $true” followed by “Set-MpPreference -DisableRealtimeMonitoring $false“. These commands will disable and then re-enable real-time monitoring for Windows Defender.

6. If none of the above steps resolve the issue, you may need to perform a clean boot to identify any conflicting software or services. To do this, press the Windows key and type “msconfig” into the search bar. Open the System Configuration utility and go to the Services tab. Check the box next to “Hide all Microsoft services” and click on “Disable all.” Then, go to the Startup tab and click on “Open Task Manager.” Disable all startup items and restart your computer.

7. If the Windows Defender service still does not start after performing a clean boot, you may need to consider reinstalling the operating system or seeking further assistance from Microsoft support.

powershell
# Check if Windows Defender service is running
$defenderService = Get-Service -Name WinDefend

if ($defenderService.Status -eq 'Running') {
Write-Host "Windows Defender service is already running."
}
else {
# Attempt to start the service
try {
Start-Service -Name WinDefend
Write-Host "Windows Defender service started successfully."
}
catch {
Write-Host "Failed to start Windows Defender service."
Write-Host "Error: $($_.Exception.Message)"
}
}


This PowerShell script checks the status of the Windows Defender service using the `Get-Service` cmdlet. If the service is already running, it displays a message stating that it’s running. Otherwise, it attempts to start the service using `Start-Service` and provides appropriate feedback.

Tips to Ensure Windows Defender Functionality and Error Prevention

Timothy Johnson